Learning Electronics

Learning Electronics

Learn to build electronic circuits

A Tan Timer Circuit Diagram

Six timing positions suited to different skin types, Timing affected by sunlight intensity

This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight. A Rotary Switch sets the timer according to six classified Photo-types (see table). A Photo resistor extends the preset time value according to sunlight brightness (see table). When preset time ends, the beeper emits an intermittent signal and, to stop it, a complete switch-off of the circuit via SW2 is necessary.

Circuit diagram:

 A Tan Timer Circuit Schematic - Circuit Diagram
Tan Timer Circuit Diagram


R1 = 47K - 1/4W Resistor
R2 = 1M - 1/4W Resistor
R3 = 120K - 1/4W Resistors
R4 = Photo resistor (any type)
R5 = 120K - 1/4W Resistors
C1 = 10µF - 25V Electrolytic Capacitors
C2 = 220nF - 63V Polyester Capacitor
C3 = 10µF - 25V Electrolytic Capacitors
D1 = 1N4148 - 75V 150mA Diodes
D2 = 1N4148 - 75V 150mA Diodes
Q1 = BC337 - 45V 800mA NPN Transistor
B1 = 3V Battery (two 1.5V AA or AAA cells in series)

IC1 = 4060 - 14 stage ripple counter and oscillator IC
IC2 = 4017 - Decade counter with 10 decoded outputs IC
SW1 = 2 poles 6 ways Rotary Switch (see notes)
SW2 = SPST Slider Switch
BZ1 = Piezo sounder (incorporating 3KHz oscillator)

Photo-typeFeaturesExposure time
I & childrenLight-eyed, red-haired, light complexion, freckly20 to 33 minutes
IILight-eyed, fair-haired, light complexion28 to 47 minutes
IIILight or brown-eyed, fair or brown-haired, light or slightly dark complexion40 to 67 minutes
IVDark-eyed, brown-haired, dark complexion52 to 87 minutes
VDark-eyed, dark-haired, olive complexion88 to 147 minutes
VIThe darkest of all136 to 227 minutes
Note that pregnant women belong to Photo-type I